Revert "autotest: disable video power tests if AC state is unexpected"

This reverts commit 9cca67a5c9d069d37c9c8d83958445fedf1f3587.

Reason for revert: break video_WebRtcPerf

Original change's description:
> autotest: disable video power tests if AC state is unexpected
> 
> BUG=chromium:723968
> TEST=video_PlaybackPerf and video_WebRtcPerf
> 
> Change-Id: I15deccbc60c942a3f9787d398134f4c85fcdecfe
> Reviewed-on: https://chromium-review.googlesource.com/517004
> Commit-Ready: Kuang-che Wu <kcwu@chromium.org>
> Tested-by: Kuang-che Wu <kcwu@chromium.org>
> Reviewed-by: Pin-chih Lin <johnylin@chromium.org>
> 

BUG=chromium:723968

Change-Id: I06e5a32538c2f22584290aefc8e94d5a74d8bdb0
Reviewed-on: https://chromium-review.googlesource.com/517842
Reviewed-by: Kuang-che Wu <kcwu@chromium.org>
Tested-by: Kuang-che Wu <kcwu@chromium.org>
diff --git a/client/site_tests/video_PlaybackPerf/video_PlaybackPerf.py b/client/site_tests/video_PlaybackPerf/video_PlaybackPerf.py
index b81a721..71d3288 100644
--- a/client/site_tests/video_PlaybackPerf/video_PlaybackPerf.py
+++ b/client/site_tests/video_PlaybackPerf/video_PlaybackPerf.py
@@ -202,13 +202,8 @@
         self._service_stopper.stop_services()
 
         self._power_status = power_status.get_status()
-        # We expect the DUT is powered by battery now. But this is not always
-        # true due to other bugs. Disable this test temporarily as workaround.
-        # TODO(kcwu): remove this workaround after AC control is stable
-        #             crbug.com/723968
-        if self._power_status.on_ac():
-            raise error.TestNAError('Still powered by AC. Skip this test')
-        # Verify that the battery is sufficiently charged.
+        # Verify that we are running on battery and the battery is sufficiently
+        # charged.
         self._power_status.assert_battery_state(BATTERY_INITIAL_CHARGED_MIN)
 
         measurements = [power_status.SystemPower(
diff --git a/client/site_tests/video_WebRtcPerf/video_WebRtcPerf.py b/client/site_tests/video_WebRtcPerf/video_WebRtcPerf.py
index 41afc34..2f4f913 100644
--- a/client/site_tests/video_WebRtcPerf/video_WebRtcPerf.py
+++ b/client/site_tests/video_WebRtcPerf/video_WebRtcPerf.py
@@ -287,14 +287,9 @@
                 service_stopper.ServiceStopper.POWER_DRAW_SERVICES)
         self._service_stopper.stop_services()
 
+        # Verify that we are running on battery and the battery is sufficiently
+        # charged.
         current_power_status = power_status.get_status()
-        # We expect the DUT is powered by battery now. But this is not always
-        # true due to other bugs. Disable this test temporarily as workaround.
-        # TODO(kcwu): remove this workaround after AC control is stable
-        #             crbug.com/723968
-        if self._power_status.on_ac():
-            raise error.TestNAError('Still powered by AC. Skip this test')
-        # Verify that the battery is sufficiently charged.
         current_power_status.assert_battery_state(BATTERY_INITIAL_CHARGED_MIN)
 
         measurements = [power_status.SystemPower(